We intend to address the problems of tolerance to peripheral tissue restricted self antigens. While the thymus appears to be the primary site for inducing tolerance to self, it is clearly not perfect in this function. Many tissue restricted antigens are not expressed by the thymus or bone marrow derived cells, and they are also not likely to be shed in sufficient quantities to be transported to the thymus by circulating macrophages or dendritic cells. It is important to determine how the immune system induces and maintains tolerance to such antigens, for immune responses to these antigens lead to devastating autoimmune syndromes such as insulin dependent diabetes and multiple sclerosis. With a detailed understanding of regulation of the immune response to self antigens, it should be possible to develop methods of treatment ot control the immune responses in organ transplant recipients and patients with autoimmune disease. Three specific aims are proposed: 1. We will determine whether mature CD4 T cells are susceptible to anergy induction in vitro using the model "signal 1 without signal 2." In vivo, studies will determine whether T cell receptor binding by superantigen versus peptide/MHC complexes on nonlymphoid antigen presenting cells can produce anergy, and whether the two types of ligands have distinct consequences with respect to tolerance induction and the physiology of the susceptibility of TcR transgenic T cells to tolerance induction. Our working hypothesis is that susceptibility is related to T lymphopenia caused by the interaction between the T cell receptor transgene and C57BL/10 background genes. This interaction may also influence the potential for CD4 cells to develop as Th1 rather that Th1 rather than Th2 cells. Our hypothesis will tested by correlating T cell numbers in TcR transgenic mice on different genetic backgrounds with susceptibility to diabetes, RT6 expression, and cytokine production. 3. Using the Ins-HA model, we plan to extend our analysis of the histology of lymphocytic infiltration into the pancreatic islets in vivo. Specifically, we would like to determine the relative contribution of antigen specific T cells versus nonspecifically recruited T cells to the immune infiltrates. Since islet infiltration can exist without progression toward diabetes, we will test whether the presence of tolerant or anergic T cells is important in preventing progression toward autoimmune diabetes. Finally, we will use in situ hybridization to determine whether changes in the patterns of cytokine production influence the progression of immune infiltrates.